Brisbane looks likely to have reached its pinnacle after yesterday's announcement of a 90-storey building on Margaret Street that, on completion, will probably remain the city's tallest.

Unless guidelines by Airservices Australia and the Civil Aviation Safety Authority change, the 274-metre 111+222 development is the highest a building can be built in Brisbane's central business district.

The restriction is not due to fears that an aircraft would physically strike the building, but rather that tall buildings could cause radar signal reflection, an Airservices spokesman said last night.

The spokesman for Airservices Australia, the agency responsible for air traffic control, said radar signal reflections and interference with summer take-off and landing flight paths into the wind were the two main issues confronting development in the CBD.

"Anything above that height interferes with the radar signals and also could conceivably cause problems for flight paths into Brisbane Airport," he said.

"Essentially it is a safety issue and CASA being the safety authority has very strict height limits that have to be met around flight path areas."

This is approved at 274m currently, though developers are apparently pushing for the original 297m or possible 300m to make it the tallest building in Australia. Many city councilors have backed the project and what it will do for Brisbane, too